TDMA radio network with provision for a group call channel for designated satellite stations

Abstract

The radio transmission system includes at least one base station (RA or RB) and at least one satellite station (M1, . . . , M7) situated in a coverage zone (ZA, ZB) of the base station in which the base station can send information to a satellite station by a down transmission channel (F RAM ), while one transmission channel is used in which the satellite stations are authorized to transmit. For establishing a group call at the request of a satellite station, the base station allocates a group call channel to the requesting station so that exchange of information can take place directly between the mobile stations which are included in the group call.

I claim: 
     
       1. A radio transmission system comprising at least one base station, each base station having a radio coverage zone, and a plurality of satellite stations at least one of which is situated in a radio coverage zone of said one base station, each base station being operative to transmit information to a satellite station in its coverage zone via an assigned time division multiplex (TDM) time slot in a down frequency transmission channel, each satellite station being operative to transmit information via an assigned TDM time slot in an up frequency transmission channel; characterized in that, upon request by said one satellite station, said one base station is operative to assign a particular TDM time slot in one of said frequency channels as a group call channel for exchange of information between satellite stations in a designated group which includes said one satellite station, without further intervention by said one base station. 
     
     
       2. A radio transmission system as claimed in claim 1, wherein the group call channel is a TDM time slot in the up frequency transmission channel of said one base station. 
     
     
       3. A radio transmission system as claimed in claim 2, comprising at least a second base station having an up frequency transmission channel which is synchronized with the up frequency transmission channel of said one base station, and wherein the group call channel is a TDM time slot which occurs concurrently in the up frequency channels of said one base station and said second base station so as to permit exchange of information between satellite stations which are located in the respective coverage zones of said one base station and said second base station.